Contours of constant GR and SR rotation angles (χ^GR + χ^SR), in disk coordinates. The position of the critical point is shown as a function of inclination for rotation caused solely by GR and SR effects (equivalent to B = B_z). The disk rotates counterclockwise (σ = 90°) in the equatorial plane, but at inclinations of i = 165° (a), 155° (b), and 140° (c) it is seen as rotating in the clockwise direction.